The overall objective of the Clinical Core is to support Project I, II, and III by establishing and maintaining a cohort of 150 HIV-1 infected women at 3 sites (Seattle, Rochester and Nairobi) over five years. The Clinical Core will also examine other co-factors that are expected to influence systemic and genital HIV viral dynamics across projects. The specific scientific objectives of the Clinical Core are: 1. To examine the effects of hormonal variation in relation to pregnancy, hormonal contraception, menopause, and hormone replacement therapy on HIV-1 viral dynamics in the blood and genital tract compartments. 2. To examine the impact of genital tract infection of HIV-1 shedding among women, and to determine whether treatment of these infections decreases endocervical viral load. 3.. To assess the impact of adherence to anti-retroviral medications on the development and pattern of genetic mutations and phenotypic resistance over time, in plasma and genital compartments. 4. To explore the association between sexual behavior, vaginal microbiology and genital HIV-1 shedding. The cohorts in Seattle and Rochester are demographically similar, and together will provide a well-characterized group for 100 men for enrollment into Projects I, II and III. An additional 50 women will be enrolled from Nairobi for a total cohort size of 150 women. The inclusion of the Nairobi cohort will add valuable insight into the dynamics of plasma and genital HIV in a population without access to anti-retroviral treatment. The vast majority of women with HIV live in parts of the world with limited or no access to anti-retroviral therapy. It is critical that we learn about co-factors that may influence the course of HIV infection in this population if we hope to design useful interventions.